Apparatus and process for making elastic composite sheet

ABSTRACT

An apparatus and process for making an elastic composite sheet including a pair of rolls adapted to bond respective surfaces of a non-stretchable sheet and a stretchable sheet and fed together into a nip of the rolls. One of the rolls is formed with ridges while the other roll is formed with grooves and the ridges are engaged with the grooves with spaces left between surfaces of the ridges and the grooves to form the non-stretchable sheet on its surface with stripe-like crests and flat troughs each defined between each pair of the adjacent crests; and the non-stretchable sheet is bonded along its troughs to the surface of the stretchable sheet.

BACKGROUND OF THE INVENTION

[0001] This invention relates to an apparatus and a process for makingan elastic composite sheet.

[0002] Japanese Patent Application Disclosure No. 1998-245757 describesa process for making a sheet-like elastic composite comprising the stepsof feeding a thermoplastic non-stretchable sheet into a nip between aheat-embossing roll formed on its peripheral surface with stripe-likeridges and grooves and a roll formed on its peripheral surface with thesimilar ridges and grooves adapted to be engaged with those of theheat-embossing roll to form the non-stretchable sheet with thecorresponding ridges and grooves, and feeding a stretchable sheettogether with the non-stretchable sheet formed with the ridges andgrooves into a nip between the embossing roll and a flat roll toheat-seal the non-stretchable sheet only along the ridges formed thereonwith the stretchable sheet.

[0003] The process described in the Japanese Patent ApplicationDisclosure No. 1998-245757 requires two separate the steps, i.e., thestep of forming the non-stretchable sheet with the ridges and groovesand the step of heat-seal the non-stretchable sheet with the stretchablesheet. On the step of forming the non-stretchable sheet with the ridgesand grooves, heat transfer inevitably occurs from the embossing roll andthe roll having the ridges and the grooves adapted to be engaged withthose of the embossing roll to substantially the whole surface of thenon-stretchable sheet. Such heat transfer hardens the non-stretchablesheet and thereby deteriorates a touch expected for this non-stretchablesheet.

SUMMARY OF THE INVENTION

[0004] It is an object of this invention to provide an apparatus formaking an elastic composite sheet enabling the elastic composite sheetto be made through the number of the steps fewer than the prior art hasrequired without deterioration of a touch expected to be presented bythe sheet.

[0005] According to one aspect of this invention, there is provided anapparatus for making an elastic composite sheet comprising a pair ofrolls opposed to each other adapted to bond respective surfaces of anon-stretchable sheet and a stretchable sheet placed one upon anotherand fed together into a nip of the pair of rolls to each other, wherein:

[0006] one of the rolls is formed on a peripheral surface thereof with aplurality of ridges projecting outward radially of the roll andextending circumferentially at predetermined intervals while the otherof the rolls is formed on a peripheral surface thereof with a pluralityof grooves recessed inward radially of the roll and extending alsocircumferentially at predetermined intervals; the ridges are engagedwith the grooves with spaces left between surfaces of the ridges and thegrooves to form the non-stretchable sheet on a surface thereof with aplurality of stripe-like crests extending in one direction and aplurality of flat troughs each defined between each pair of the adjacentcrests; and the non-stretchable sheet is bonded along the troughs to thesurface of the stretchable sheet.

[0007] According to another aspect of this invention, there is provideda process for making an elastic composite sheet comprising a step offeeding a non-stretchable sheet and a stretchable sheet placed one uponanother together into a nip of a pair of rolls opposed to each other andthereby bonding respective surfaces of the non-stretchable sheet and thestretchable sheet to each other, wherein:

[0008] one of the rolls is formed on a peripheral surface thereof with aplurality of ridges projecting outward radially of the roll andextending circumferentially at predetermined intervals while the otherof the rolls is formed on a peripheral surface thereof with a pluralityof grooves recessed inward radially of the roll and extending alsocircumferentially at predetermined intervals and the process comprisesthe steps of engaging the ridges with the grooves with spaces leftbetween surfaces of the ridges and the grooves to form thenon-stretchable sheet on a surface thereof with a plurality ofstripe-like crests extending in one direction and a plurality of flattroughs each defined between each pair of the adjacent crests; andbonding the non-stretchable sheet along the troughs to the surface ofthe stretchable sheet.

[0009] The apparatus and process for making the elastic composite sheetas has been described hereinabove is advantageous in that thenon-stretchable sheet can be formed on its surface with a plurality ofstripe-like crests extending in one direction and a plurality of troughseach defined between each pair of the adjacent crests extending also inthe one direction and simultaneously the troughs of the non-stretchablesheet can be bonded to the surface of the stretchable sheet merely byfeeding the non-stretchable sheet together with the stretchable sheetinto the nip between a pair of rolls. In this way, the elastic compositesheet can be made through the minimum number of the steps. The ridgesand the grooves formed on the respective rolls are engaged one withanother in non-contact fashion and therefore it is not apprehended thatheat might be transferred to the crests of the non-stretchable sheet anddeteriorate a touch presented by these crests of the non-stretchablesheet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a perspective view of an apparatus according to thisinvention for making an elastic composite sheet;

[0011]FIG. 2 is a sectional view taken along line A-A in FIG. 1; and

[0012]FIG. 3 is a perspective view of the elastic composite sheetobtained by the apparatus and a process according to this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Details of an apparatus according to this invention for making anelastic composite sheet will be more fully understood from thedescription given hereunder with reference to the accompanying drawings.

[0014]FIG. 1 is a perspective view of an apparatus 1 for making anelastic composite sheet and FIG. 2 is a sectional view taken along lineA-A to show an important part of the apparatus. Referring to FIG. 1,upstream of the apparatus 1, there are provided feeders 4, 5 of anon-stretchable sheet 2 and a stretchable sheet 3, respectively.Downstream of the apparatus 1, there is provided a take-up roller 6 fora finished composite sheet 12. The apparatus 1 comprises a pair of rolls1 a, 1 b vertically opposed to each other.

[0015] The lower roll 1 a is formed on its peripheral surface with aplurality of ridges 7 projecting outward radially of the roll 1 a. Theupper roll 1 b is formed on its peripheral surface with a plurality ofgrooves 8 recessed inward radially of the roll 1 b and adapted to beengaged with the ridges 7 on the lower roll 1 a. The ridges 7 and thegrooves 8 extend circumferentially around an axis of the rolls 1 a, 1 b.With the apparatus 1 of this invention, spaces 11 are left betweensurfaces of the ridges 7 and grooves 8 when the ridges 7 on the roll 1 aare engaged with the grooves 8 on the roller 1 b, as will be apparentfrom FIG. 2. At least one of these rolls 1 a, 1 b is heated to seal thetwo sheets 2, 3 with each other. It is also possible to arrange theridges 7 and the grooves 8 to extend axially of these rolls 1 a, 1 b.

[0016] The non-stretchable sheet 2 and the stretchable sheet 3 are fedfrom the respective feeders 4, 5 so that the non-stretchable sheet 2 mayoverlie the stretchable sheet 3. These sheets 2, 3 are laminated witheach other in the course defined between the feeders 4, 5 and theapparatus 1 and then enter a nip between the pair of rolls 1 a, 1 b. Inthis contact zone defined between the ridges 7 and the grooves 8 on therolls 1 a, 1 b, respectively, the non-stretchable sheet 2 lies adjacentthe grooves 8 and the stretchable sheet 3 lies adjacent the ridges 7.These sheets 2, 3 are stretched by the ridges 7. The ridges 7 and thegroove 8 are not in surface-contact relationship and therefore thenon-stretchable sheet 2 is not heat-sealed with the stretchable sheet 3.The non-stretchable sheet 2 and the stretchable sheet 3 are heat-sealedwith each other on flat surfaces 9, 10 of the respective rolls 1 a, 1 bdefined between each pair of adjacent ridges 7 and defined between eachpair of adjacent grooves 8, respectively.

[0017] Having left the apparatus 1, regions of the stretchable sheet 3having been stretched by engagement between the ridges 7 and the grooves8 substantially restore their initial flatness under an elasticity ofthe sheet 3 while the non-stretchable sheet 2 is formed thereon with aplurality of stripe-like crests 2 a extending in one direction. Thenon-stretchable sheet 2 is formed by the flat surfaces 9, 10 of therespective rolls 1 a, 1 b between each pair of the adjacent crests 2 awith a practically flat trough 2 b. These flat troughs 2 b of thenon-stretchable sheet 2 is heat-sealed with the stretchable sheet 3.

[0018] In the apparatus 1, a value corresponding to an arc dimension L2of the ridge 7 divided by a chord of the ridge connecting opposite endsof the arc should be in a range of 1.5˜4.5. At the value less than 1.5,the arc dimension of the crest 2 a formed on the surface of thenon-stretchable sheet 2 would be insufficient to obtain a desiredstretch ratio of the composite sheet 12. At the value higher than 4.5,depending on the maximum stretch ratio of the stretchable sheet 3, thecrest 2 a of the non-stretchable sheet 2 would slacken even after themaximum stretch ratio has been exceeded. Consequently, a touch presentedby the non-stretchable sheet 2 would be deteriorated.

[0019] In the apparatus 1, a value corresponding to the chord dimensionL1 of the ridge 7 divided by a dimension L3 between a pair of theadjacent ridges 7, more specifically, between one end of the one ridge 7and one end of the adjacent ridge 7 opposed to each other should be in arange of 0.1˜0.5. At the value less than 0.1, the dimension of therespective flat surfaces 9, 10 formed on the rolls 1 a, 1 b,respectively, would be insufficient to achieve a reliable sealingbetween the non-stretchable sheet 2 and the stretchable sheet 3. At thevalue higher than 0.5, the number of relatively rigid seal lines wouldincrease on the non-stretchable sheet 2 as well as on the stretchablesheet 3, resulting in a deteriorated touch of the composite sheet 12.

[0020] A stretch ratio of the composite sheet 12 made by the apparatus 1can be calculated according to the following equation:

Stretch ratio={(L 2+L 3/L 1+L 3)−1}×100

[0021] where

[0022] L1=chord dimension of ridge 7

[0023] L2=arc dimension of ridge 7

[0024] L3=dimension between adjacent ridges 7, 7.

[0025] The stretch ratio of the composite sheet 12 should be in a rangeof 33˜318%.

[0026]FIG. 3 is a perspective view of the elastic composite sheet 12made by the apparatus 1. The composite sheet 12 comprises thenon-stretchable sheet 2 and the stretchable sheet 3 laminated with eachother wherein the non-stretchable sheet 2 is formed thereon with aplurality of the crests 2 a extending in one direction and a pluralityof the practically flat troughs 2 b defined between each pair of theadjacent crests 2 a and extending also in the one direction. Thenon-stretchable sheet 2 is sealed at the troughs 2 b with the surface ofthe stretchable sheet 2 and the crests 2 a of the non-stretchable sheet2 are not sealed with the surface of the stretchable sheet 2. Thenon-stretchable sheet 2 as well as the stretchable sheet 3 can bestretched by the arc dimensions of the crests 2 a as the composite sheet12 is stretched transversely of the direction in which the crests 2 aformed on the non-stretchable sheet 2 extend.

[0027] The non-stretchable sheet 2 may be formed by a nonwoven fabric ofthermoplastic synthetic resin fiber. The nonwoven fabric may be selectedfrom those of various types such as spun lace-, needle punch-, meltblown-, thermal bond-, spun bond- or chemical bond-type. Thenon-stretchable sheet has a basis weight preferably of 15˜80 g/m², morepreferably of 20˜60 g/m². Component fiber for the nonwoven fabric may beselected from various types of thermoplastic fiber such as polyolefine,polyester and polyamide fibers, and conjugated fiber such aspolyethylene/polypropyrene or polyester conjugated fiber.

[0028] The stretchable sheet 3 may be formed by elastomer ofthermoplastic synthetic resin. The elastomer may be selected from agroup including polyolefine, polyester, polyamide and polyurethaneelastomers.

[0029] Bonding between the non-stretchable sheet 2 and the stretchablesheet may be carried out using the heat-sealing or suitable adhesivesuch as hot melt adhesive. For the case in which the adhesive is used,the non-stretchable sheet 2 and the stretchable sheet 3 are fed to theapparatus 1 after the opposed surfaces of these two sheets 2, 3 havebeen bonded to each other. Travelling through the apparatus 1 betweenthe ridges 7 and the grooves 8 thereof, the non-stretchable sheet 2 isforcibly stretched by the ridges 7 and broken. Contraction of thestretchable sheet 3 causes the non-stretchable sheet 2 also to becontracted and thereupon the composite sheet 12 is formed with gathers.

What is claimed is:
 1. An apparatus for making an elastic compositesheet comprising a pair of rolls opposed to each other adapted to bondrespective surfaces of a non-stretchable sheet and a stretchable sheetplaced one upon another and fed together into a nip of said pair ofrolls to each other, wherein: one of said rolls is formed on aperipheral surface thereof with a plurality of ridges projecting outwardradially of said roll and extending circumferentially at predeterminedintervals while the other of said rolls is formed on a peripheralsurface thereof with a plurality of grooves recessed inward radially ofsaid roll and extending also circumferentially at predeterminedintervals; said ridges are engaged with said grooves with spaces leftbetween surfaces of said ridges and said grooves to form saidnon-stretchable sheet on a surface thereof with a plurality ofstripe-like crests extending in one direction and a plurality of flattroughs each defined between each pair of the adjacent crests; and saidnon-stretchable sheet is bonded along said troughs to the surface ofsaid stretchable sheet.
 2. The apparatus according to claim 1, wherein avalue corresponding to an arc dimension of each said ridge as measuredin a section of said rolls divided by a chord dimension of this ridgedefined between opposite ends of said arc is in a range of 1.5˜4.5. 3.The apparatus according to claim 1, wherein a value corresponding tosaid chord dimension of said ridge as measured in a section of saidrolls divided by a dimension between each pair of the adjacent ridges asmeasured between adjacent ones of respective ends of these two ridges isin a range of 0.1˜0.5.
 4. The apparatus according to claim 1, wherein astretch ratio of said composite sheet as obtained transversely of thedirection in which said crests extend is given by an equation: Stretchratio={(arc dimension of ridge+dimension between each pair of adjacentridges as measured between adjacent ones of respective ends of these tworidges/chord dimension of ridge+said dimension between each pair ofadjacent ridges as measured between adjacent ones of respective ends ofsaid two ridges)−1}×100; and said stretch ratio is in a range of33˜318%.
 5. The apparatus according to claim 1, wherein saidnon-stretchable sheet is formed by a nonwoven fabric of thermoplasticsynthetic resin fiber while said stretchable sheet is formed byelastomer made of thermoplastic synthetic resin and said non-stretchablesheet and said stretchable sheet are heat-sealed with each other by saidpair of rolls.
 6. A process for making an elastic composite sheetcomprising a step of feeding a non-stretchable sheet and a stretchablesheet placed one upon another together into a nip of a pair of rollsopposed to each other and thereby bonding respective surfaces of saidnon-stretchable sheet and said stretchable sheet to each other, wherein:one of said rolls is formed on a peripheral surface thereof with aplurality of ridges projecting outward radially of said roll andextending circumferentially at predetermined intervals while the otherof said rolls is formed on a peripheral surface thereof with a pluralityof grooves recessed inward radially of said roll and extending alsocircumferentially at predetermined intervals, and said process comprisesthe steps of: engaging said ridges with said grooves with spaces leftbetween surfaces of said ridges and said grooves to form saidnon-stretchable sheet on a surface thereof with a plurality ofstripe-like crests extending in one direction and a plurality of flattroughs each defined between each pair of the adjacent crests; andbonding said non-stretchable sheet along said troughs to the surface ofsaid stretchable sheet.